The treatment of chronic pain has long been a troublesome area of medical practice. “Chronic pain” is a diagnosis that is less a true diagnosis of the physiological condition than a symptomatic diagnosis describing a chronic condition. The diagnosis often results after multiple interventions by licensed medical professionals using surgery, drugs, manipulation, stretching, chiropractic, and other modalities without substantial and/or permanent relief of the patient's pain. “Chronicity” is generally described as pain lasting for greater than 6 months, and in some cases, the time period is described as greater than 12 months.
Once a patient is diagnosed as suffering from chronic pain, often the patient is sent to a licensed professional, generally a physical therapist, who treats the patient 2 to 3 times per week in a clinic. One very common pain-treatment device is an interferential (IF) unit, which administers electrical pulses to and around the painful area. During treatment, the patient lies down and 2 to 4 electrodes are applied around the area of pain. The interferential unit then applies electrical pulses via two channels to the treatment area (typically about 5,000 to 8,500 pulses per second) for, typically, 20 to 40 minutes. The output of the two channels is configured so that the electrical currents from the two separate channels perpendicularly intersect each other in the mid-painful area, and so that the frequency of pulses differs between the channels, thereby allowing the two currents of differing orientation and frequency to interact. An exemplary interferential unit is the INTERFERENZ 5, available from Bosch.
The body is both an insulator and a conductor of electricity. At a pulse frequency of 4,000 to 5,000 pulses per second, the resistance imposed by the skin is reduced and the current can stimulate more nerves beneath the outer layer of skin. The body seems to modify the current from the two channels of an interferential unit. The resulting current from the intersection creates a new resultant waveform that alternates in amplitude and form. As a result of the current modifications the patient receives more sensory stimulation, which can relieve the pain. Generally there is a longer “carryover” period, post-treatment, in which the patient is relatively pain free, than what is achieved using other types of devices with less electrical output.
One significant shortcoming of a conventional interferential unit is its lack of portability. Viable interferential units have required alternating current for operation, as different batteries that have been tried that would enable the unit to be portable (typical 9 volt systems, including both disposable alkaline batteries and rechargeable Ni—Cd batteries) have been inadequate (some exhaust the system in less than one minute). As such, the typical setting for interferential treatment has been in a clinic, where the unit can be plugged into a wall outlet, rather than in the home or at the time of need.
One alternative unit for the treatment of chronic pain is a Transcutaneous Electrical Nerve Stimulator (TENS) device. The TENS unit is a dual channel device that typically delivers 0.5 to 200 pulses per second at a pulse width of between about 50 and 250 microseconds. The patient receives 2 to 4 electrodes around the area of pain for as long as needed. The amplitude of the TENS wave is adjusted until the patient feels sensory input that is pleasurable and not uncomfortable. If the TENS treatment benefits the patient, the physician/therapist often recommends that a TENS unit be rented and/or purchased for the patient for home use, particularly for sessions between interferential treatments.
A TENS device uses a 9 volt battery, which is sufficient because of the relative low output required for the use of this device. The TENS unit typically is a truly portable device that that the patient can wear and use on a 24 hour basis without the constraint of a lack of electrical energy due to insufficient battery capabilities. An exemplary TENS unit is the EPIX XL unit, available from EMPI, Inc.
Unfortunately, a TENS unit is generally not as effective as an interferential unit and rarely has the carryover effect achieved with the IF units. Due to this lack of “carryover relief,” it is not unusual for a patient to wear a TENS unit continuously initially, then less if the underlying condition improves. Also, in many instances patients' pain relief is limited to areas between the electrodes of the TENS unit: i.e., “deep” pain (such as sciatica or other joint pain) is not relieved.